Аннотация

A numerical solution is presented for the heat transfer in laminar compressible flow in a tapered channel under oscillating flow. The heat transfer has been studied for a situation of a tapered channel with insulated walls and two extreme temperatures at both ends, with Helium gas, simulating the conditions of a Pulse Tube cryocooler. Two kinds of tapered channel were examined: convergent and divergent, which describe the hot and cold side. The convective axial heat loss was calculated and found to be non-zero despite the periodic nature of the flow. It was calculated for a wide range of tapered channel angles. This shows an optimal angle existing that gives the minimum convective axial heat loss, at the convergent profile achieve a 80% improvement while at the divergent profile a negligible improvement occur.
A CFD solution helps determine the effects of compressibility on the flow and heat transfer. Axial heat loss and the flow characteristics numbers, Valensi (Va) and Reynolds (Re), are calculated. Analysis of these results helps explain the improvement due to the use of a tapered channel.